Field of the Disclosure
The present disclosure relates generally to processing systems and, more particularly, to supplying power to processing systems.
Description of the Related Art
Automatic test equipment (ATE) is used to test processing systems such as a system-on-a-chip (SOC) after fabrication and prior to installation in a product. For example, automated testing may be used to determine the operating frequencies of components of the SOC under different operating loads for a given applied voltage. A typical ATE includes a very high-quality voltage supply that can maintain a constant applied voltage within a very narrow tolerance for a wide range of operating loads. However, the system-level voltage supplies that are used in products such as desktop computers, laptop computers, tablets, smart phones, and the like are not able to maintain the same voltage tolerances over the same range of operating loads. For example, if the load on an SOC suddenly increases from a very low level to a relatively high level, the current drawn by the components of the SOC increases and the voltage provided to components of the SOC falls, a phenomenon known as “voltage droop.” The operating frequencies of the components of the SOC also fall when the voltage droops.
The amount of voltage droop depends on the characteristics of the power supply and the load on the SOC. Virtually every product that is shipped to a consumer has a slightly different power supply and will experience different operating loads over its lifetime. Thus, the power supply characteristics and the operating loads of each consumer product are not precisely known and may change over the lifetime of the product. Consequently, an SOC that is rated for a particular operating frequency must include a voltage margin to ensure that the actual operating frequency of the SOC does not fall below the rated value during voltage droop. The voltage margin is typically set by assuming a worst-case scenario, e.g., the largest expected voltage droop under the highest operating loads. During normal operation, e.g., under moderate or light operating loads, the voltage margin is unnecessary and may therefore represent wasted power or an operating frequency in excess of the rated value.